Let's assume that the size of the design draft that my sister gave us is 750 * 1340. Combined with the dynamic font size attribute, design draft size and collaboration process between the front end and design on the html element of the home page of Netease and Taobao mobile terminal, they are generally divided into the following two types:

1. Netease: Introduce this code at the beginning of the import page. Used for dynamic calculation font size

  (function (){
       var docEl = doc.documentElement,
    isIOS = navigator.userAgent.match(/\(i[^;]+;( U;)? CPU.+Mac OS X/),
    dpr = isIOS ? Math.min(win.devicePixelRatio, 3) : 1,
    dpr = window.top === window.self ? dpr : 1, //Disable scaling when referenced by iframe
    dpr = 1,
    scale = 1 / dpr,
    resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize';
	docEl.dataset.dpr = dpr;
	var metaEl = doc.createElement('meta');
	metaEl.name = 'viewport';
	metaEl.content = 'initial-scale=' + scale + ',maximum-scale=' + scale + ', minimum-scale=' + scale;
	docEl.firstElementChild.appendChild(metaEl);
	var recalc = function() {
	var width = docEl.clientWidth;
	if (width / dpr > 750) {
	width = 750 * dpr;
	}
	// Multiply by 100, PX: REM = 100: 1
	docEl.style.fontSize = 100 * (width / 750) + 'px';
	};
	recalc()
	if (!doc.addEventListener) return;
	win.addEventListener(resizeEvt, recalc, false);
  
  
  })(document, window);
  
  <style>
       body{
	     width: 750px;
		 height:640px;
	   }
	   /***
	       Basis for conversion after introduction
	 */
		      body{
			    width:7.5rem;
				height:6.4rem;
			  }
	  </style>
	  <script>
			 var recalc = function (){
			   var width = docEl.clientWidth;
			   if(width / dpr >750) {
				  width = 750 * dpr;
			   }
			   decEl.style.fontSize = 100* (width/750) + 'px'
		 	}
	</script>

2, Taobao practice (Recommended practice, especially app embedded page): Import: the following code is introduced at the beginning of the page for dynamic calculation of font size, or put into a file separately, or import a file

; (function(win, lib) { var doc = win.document; var docEl = doc.documentElement; var metaEl = doc.querySelector('meta[name="viewport"]'); var flexibleEl = doc.querySelector('meta[name="flexible"]'); var dpr = 0; var scale = 0; var tid; var flexible = lib.flexible || (lib.flexible = {});

if (metaEl) {
    var match = metaEl.getAttribute('content').match(/initial\-scale=([\d\.]+)/);
    if (match) {
        scale = parseFloat(match[1]);
        dpr = parseInt(1 / scale);
    }
} else if (flexibleEl) {
    var content = flexibleEl.getAttribute('content');
    if (content) {
        var initialDpr = content.match(/initial\-dpr=([\d\.]+)/);
        var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/);
        if (initialDpr) {
            dpr = parseFloat(initialDpr[1]);
            scale = parseFloat((1 / dpr).toFixed(2));
        }
        if (maximumDpr) {
            dpr = parseFloat(maximumDpr[1]);
            scale = parseFloat((1 / dpr).toFixed(2));
        }
    }
}

if (!dpr && !scale) {
    var isAndroid = win.navigator.appVersion.match(/android/gi);
    var isIPhone = win.navigator.appVersion.match(/iphone/gi);
    var devicePixelRatio = win.devicePixelRatio;
    if (isIPhone) {
        // Under iOS, for 2 and 3 screens, use 2-fold scheme, and for the rest, use 1-fold scheme
        if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
            dpr = 3;
        } else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)) {
            dpr = 2;
        } else {
            dpr = 1;
        }
    } else {
        // Under other equipment, the scheme of 1 times is still used
        dpr = 1;
    }
    scale = 1 / dpr;
}

docEl.setAttribute('data-dpr', dpr);
if (!metaEl) {
    metaEl = doc.createElement('meta');
    metaEl.setAttribute('name', 'viewport');
    metaEl.setAttribute('content', 'initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no');
    if (docEl.firstElementChild) {
        docEl.firstElementChild.appendChild(metaEl);
    } else {
        var wrap = doc.createElement('div');
        wrap.appendChild(metaEl);
        doc.write(wrap.innerHTML);
    }
}

function refreshRem() {
    var width = docEl.getBoundingClientRect().width;
    // Adapter plate
    if (width / dpr > 540) {
        width = 540 * dpr;
    }
    var rem = width / 10;
    docEl.style.fontSize = rem + 'px';
    flexible.rem = win.rem = rem;
}

win.addEventListener('resize', function() {
    clearTimeout(tid);
    tid = setTimeout(refreshRem, 300);
}, false);
win.addEventListener('pageshow', function(e) {
    if (e.persisted) {
        clearTimeout(tid);
        tid = setTimeout(refreshRem, 300);
    }
}, false);

if (doc.readyState === 'complete') {
    doc.body.style.fontSize = 12 * dpr + 'px';
} else {
    doc.addEventListener('DOMContentLoaded', function(e) {
        doc.body.style.fontSize = 12 * dpr + 'px';
    }, false);
}


refreshRem();

flexible.dpr = win.dpr = dpr;
flexible.refreshRem = refreshRem;
flexible.rem2px = function(d) {
    var val = parseFloat(d) * this.rem;
    if (typeof d === 'string' && d.match(/rem$/)) {
        val += 'px';
    }
    return val;
}
flexible.px2rem = function(d) {
    var val = parseFloat(d) / this.rem;
    if (typeof d === 'string' && d.match(/px$/)) {
        val += 'rem';
    }
    return val;
}